Stop The Water Loss – Adding a Shut Off Valve to Your RV Freshwater Overflow

When we first started full-timing in our Forest River travel trailer, we encountered one of our first mysteries. We’d stop, dump tanks, fill our fresh water, and a ways down the road notice our water tank was reading 1/3 to 2/3 full. Somehow, our Wildwood was losing water!

Then, one day, we figured it out. There is a hose attached to your freshwater tank, which lets air escape as you are filling it with fresh water. The way things are put together, this hose can start to have water in it while you’re driving down the road, and a siphon is created. Before you know it, your camper has lost around half of your freshwater, dumping your liquid gold on to the ground.

Believe it or not, one solution is amazingly simple, and with only a handful of inexpensive parts. Here’s what you’ll need, in order of assembly.

A simple hose clamp. This goes on first, before jamming the next piece in to your overflow/air outlet tube.
You will need to verify your tubing size coming from your camper. Ours was 1/2″, but your tube may be different. Our tube comes straight down, so we chose an elbow shape to make it easier to reach the next piece. You can go with a straight version if preferred.

To install, simply shove this piece in to your air outlet tube, and tighten the above clamp using a flat-head screw driver.

Elbo tube. This is your handy new shut-off valve. It will screw on to the above installed adapter, just like it would on a garden hose, giving you an On/Off switch to your air outlet tube.
Water shut-off valve on RV freshwater air outlet

The end result. A shut-off valve on RV freshwater air outlet

Once all pieces are attached, you are ready to re-fill your tank. Make sure you open your new valve before filling. If you neglect opening the valve, air pressure that used to escape through the air tube will instead, after a minute or so, force a nice splash of water back out of your tank, soaking you. Trust us. We know!

Once your tank is filled and the water starts running out the overflow as it always has, you simply turn your spiffy new valve and stop the flow. Voila! No more losing water from your overflow line.

Have you tried this, or have another great solution? Let us know in the comments!


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